Sand castle worms provide another common patter seen in the tidepool areas. They seem to only grow in certain areas. They tend to thrive in the lower parts of the tidepool area and in places protected from direct wave action but high water flow. Sand Castle worms are filter feeders in that they extend feeding parts into the water column to capture food. They live in tubes built out of sand that they use for protection.
The most obvious physical factor is the availability of sand. If there is no sand, there is no material for the animal to build its home. These animals also cannot move around to collect their own sand. Sand must be provided for them. Where in the tidepool environment can these worms capture sand without moving around?
Fast moving water is the mechanism these animals use to get the sand they need. Water moving at a sufficient velocity can carry sand particles a limited distance from the source. Sand Castle worms will live in places where there is fast moving water that is close to a source of sand. This explanation however is only partially true. If these animals require fast moving water near sand, why are they not seen in exposed places like mussels and barnacles?
The reason lies in the strength of their home. These tubes are strong enough to withstand some physical pressures but these tubes are not strong enough to withstand the power and force of direct wave action unlike mussels and barnacles. These animals therefore must live in places not exposed to direct wave action but still have plenty of water to carry the necessary sand and food. These animals are typically found in surge channels near sandy areas in the lower tide zone.